A ballast circuit is provided. The ballast circuit comprises a first lamp set, a second lamp set, a detection circuit, and a latch circuit. The first lamp set comprises a first inductor and a plurality of containing areas. The second lamp set comprises a second inductor and at least one containing area. The detection circuit is configured to receive a direct current (DC) voltage and coupled to the containing areas of the first and second lamp sets so that the detection circuit, the first inductor, the second inductor, and a plurality of lamps contained in the containing areas are in a series connection and generate a first signal. The latch circuit is coupled to the detection circuit and configured to selectively start in response to the first signal.